The crystalline lens of the eye is a transparent structure that is suspended immediately behind the iris, which brings rays of light to a focus on the retina. The lens contains both soluble and insoluble proteins; together they constitute 35 percent of the wet weight of the lens. In a young, healthy lens, the soluble proteins, commonly referred to as crystallins, constitute 90 percent of the lens proteins. During the aging process, the lens crystallins form insoluble aggregates, which, at least in part, account for the decreased deformability of the lens nucleus, which characterizes presbyopia, the loss of the eye's ability to change focus to see near objects. The formation of insoluble aggregates of lens crystallins in presbyopia is believed to be an early stage in the formation of age-related cataracts.
Cataracts are defined by cloudiness or opacification in the crystalline lens of the eye. As an individual ages, cataracts form as the crystallins present in the lens are converted into aggregates, resulting in increased lens opacity. Specifically, there is a progressive decrease in the concentration of the soluble chaperone, α-crystallin, in human lens nuclei with age, as it becomes incorporated into high molecular weight aggregates and insoluble protein. The presence of aggregates compromises the health and function of the lens and left untreated, cataracts can lead to substantial vision loss or even blindness. Presently, the most common treatment for cataracts is surgery.
Crystallins are structural proteins most highly expressed in the lens fiber cells of the vertebrate eye. The crystallins are divided into two subfamilies: the α-crystallins (αA and αB) which are members of the small heat shock protein superfamily, also functioning as structural proteins and molecular chaperones; and the evolutionarily-linked superfamily of β- and γ-crystallins which function primarily as structural proteins in the lens, and contribute to the transparency and refractive properties of lens structure. In addition to their role in cataract development, αA-crystallin and αB-crystallin have been implicated in neurodegenerative diseases, like Alexander's disease, Creutzfeldt-Jacob disease, Alzheimer's disease and Parkinson's disease.
U.S. Patent Application 2008/0227700 describes deaggregation of proteins using peptides having chaperone activities as a therapeutic treatment. Specifically, αB peptides were used to deaggregate pH-induced aggregates of β-crystallin as measured by light scattering. Provision of a continuous supply of alpha crystallins into the lens is a challenge. What is needed are alternative methods suitable for the deaggregation of crystallins for the inhibition and/or reversal of cataracts and presbyopia.